$-7ab + 8ac - a + 2 = -b + 4$ Solve for $a$.
Answer: Combine constant terms on the right. $-7ab + 8ac - a + {2} = -b + {4}$ $-7ab + 8ac - a = -b + {2}$ Notice that all the terms on the left-hand side of the equation have $a$ in them. $-7{a}b + 8{a}c - 1{a} = -b + 2$ Factor out the $a$ ${a} \cdot \left( -7b + 8c - 1 \right) = -b + 2$ Isolate the $a$ $a \cdot \left( -{7b + 8c - 1} \right) = -b + 2$ $a = \dfrac{ -b + 2 }{ -{7b + 8c - 1} }$ We can simplify this by multiplying the top and bottom by $-1$. $a= \dfrac{b - 2}{7b - 8c + 1}$